The present disclosure relates to image reading devices, image forming apparatuses, and image reading methods.
An image reading device reads an image of an original document with a photodetector that detects light emitted by a light source and then reflected by the original document. Such an image reading device is used as a scanner and also as a component of an image forming apparatus, such as a multi-function peripheral, a copier, and a facsimile machine.
Even when an image reading device reads the same original document, the amount of light detected by the photodetector may fluctuate for each reading operation. For example, the amount of light detected by the photodetector may fluctuate with changes in the ambient conditions or in the light source, the optical system, and/or the photodetector. To address the above, the image reading device typically performs shading correction by using a density reference plate to suppress the fluctuations in the amount of light.
Unfortunately, when the optical path from the light source to the photodetector is contaminated, appropriate shading correction is not possible. Some image reading devices may correct data with secondary white reference data in the case where the optical system is contaminated. Such an image reading device performs shading correction by using the white reference data obtained by reading the density reference plate in the case where the scanning optical system is not contaminated. However, in the case where the scanning optical system is contaminated with paper dust or the like, the shading correction is performed by using the secondary white reference data stored in advance in non-volatile memory.